1. Field of the Invention
This invention relates to a multilayered hemoglobin concentration-determining material for determining the hemoglobin concentration in aqueous solutions, especially blood hemoglobin concentration, which is an important test item in the field of medical, clinical or physiological hematology.
2. Development of the Invention
As is well known, blood is composed of plasma and cell components (e.g., erythocytes, leukocytes, thrombocytes, etc.).
The concentration of hemoglobin in whole blood is a particularly important analytical item in hematology as well as the number of erythocytes and hematocrit.
As one method for determining the hemoglobin concentration in aqueous solutions, e.g., blood (hereinafter abbreviated Hb), there is known the method of measuring the absorbance of a definite volume of hemolytic or non-hemolytic dilutions and calculating the Hb concentration based on the thus obtained data. However, this conventional method has the defects that it requires a long time and complicated wet procedures.
Another method of determining the blood hemoglobin concentration uses a dry sheet and is known as the Tallqvist method (T. W. Tallqvist, Z. Klin. Med., 40, 137, 1900). This method involves saturating a water-absorbing paper (e.g., filter paper) with a blood sample, and measuring the reflective optical density thereof.
Japanese Pat. application (OPI) No. 143885/77 (corresponding to U.S. Pat. No. 4,057,394) discloses a modified Tallqvist method of determining the blood hemoglobin concentration using a sheet-like material (the term "OPI" as used herein refers to a "published unexamined Japanese patent application"). This method involves preparing a blood-absorbing matrix by impregnating a porous medium such as a filter paper or textile with particles having a high refractive index, such as titanium oxide particles, saturating this matrix with a blood sample, and measuring the reflectivity thereof. This patent specification also describes a method of using the matrix adhesively laminated to a hydrophobic carrier like a polyester film. It is clear, however, that in such cases means for releasing and removing air contained in the blood matrix are necessary to attain good accuracy.
This specification further gives an experimental example relating to an Hb concentration-determining method using a multilayered analytical element as described in DT-OS No. 2,882,760, which element is formed by coating an enzyme- and color reagent-containing gelatin layer on a film base, then coating thereon a cellulose acetate layer containing dispersed therein titanium dioxide fine particles, further coating thereon a cellulose acetate layer containing diatomaceous earth and salicyclic acid, followed by drying. A blood sample is applied to the upper surface of the thus formed multi-layered product to saturate the same and reflectivity is measured from above the upper surface thereof using a reflective spectrograph, the blood hemoglobin concentration thus being determined.
The two above-described methods relate to applying a blood sample to a porous membrane containing light-scattering particles such as titanium oxide particles, and measuring reflective optical density from the blood sample-applied side.